In the latest version 24.7.8, once the lan port and wan port are bridged, I cannot log in to the management interface of the lan port immediately. Is it a bug, or is this problem caused by my wrong settings? Please ask professionals for guidance.
Are you trying to setup a transparent filtering bridge? or ... ?
When a NIC is a member of a bridge, you can no longer use it as a numbered interface, so you'd have to assign the new bridge to an interface, with an IP address, and use that for management access - see https://docs.opnsense.org/manual/how-tos/transparent_bridge.html , particularly steps 4 and 9
Also it is generally a good choice to have a third interface for out of band management.